[nsp] known networks for broadcast ping attacks

Thu Jul 31 03:29:21 UTC 1997

Maybe, I'm not completely understanding this, but
from my own testing, it seems to me that, when I do this without
regard to ip directed broadcast, I get one response back from the closest
interface, but perhaps they are using source routing or something
to cause this?

In message <19970730211625.11611 at texas.net>, Edward Henigin writes:
>
>	this does work as you'd expect (it prevents the cisco
>from framing an IP broadcast packet into an ethernet broadcast
>frame)  BUT unfortunately it can break Windows networking, as well
>as BOOTP/DHCP, depending on how you're set up.
>
>	but if you're not using one of the above (routed), then
>by all means, 'no ip directed-broadcast' is an excellent way to go..
>
>--
>On Wed, Jul 30, 1997 at 02:52:14PM -0700, Craig A. Huegen said:
>> On Wed, 30 Jul 1997, Jeffrey S. Curtis wrote:
>> 
>> ==>(And to answer the proverbial "how do I configure my router for that"
>> ==>in advance, the answer is that, at least on my boxes, the not-allowing-
>> ==>broadcast-pings-through-as-broadcasts-onto-the-target-media thing is on
>> ==>by default.  Source address filtering, however, is not.)
>> 
>> For Ciscos, "no ip directed-broadcast" on your interfaces will
>> prevent remote devices from sending directed broadcasts.  No guarantees
>> about applications it might break, though.
>> 
>> /cah
>

---
Jeremy Porter, Freeside Communications, Inc.      jerry at fc.net
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